CVE-2018-20803: 
MongoDB vulnerability analysis and mitigation

CVE-2018-20803 is a denial of service vulnerability affecting MongoDB Server that was discovered in 2018. The vulnerability affects multiple versions of MongoDB Server including v4.0 versions prior to 4.0.5, v3.6 versions prior to 3.6.10, and v3.4 versions prior to 3.4.19. The issue was assigned a CVSS v3.1 base score of 6.5 (Medium severity) (NVD).

The vulnerability is classified as CWE-835 (Loop with Unreachable Exit Condition - 'Infinite Loop'). When an authorized user performs specially crafted database queries, it can cause the system to enter an infinite loop during mathematics processing while retaining locks. The vulnerability has a CVSS v3.1 vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating network accessibility, low attack complexity, and requiring low privileges (MongoDB Issue).

The primary impact of this vulnerability is denial of service. When successfully exploited, the vulnerability can cause the database to become unresponsive due to infinite loops in mathematics processing while maintaining locks, potentially affecting system availability (NVD).

The vulnerability requires an attacker to be an authorized user with permissions to perform database queries. The attack can be executed remotely over the network with low attack complexity (NVD).

The vulnerability has been fixed in MongoDB Server versions 4.0.5, 3.6.10, and 3.4.19. Users are advised to upgrade to these or later versions to mitigate the vulnerability (MongoDB Issue).